The invention relates to a process for the production of a multi-layer paint coating on the surface of a substrate, in which
(1) a pigmented base paint containing crosslinked polymer microparticles and a cellulose ester is applied to the surface of the substrate PA0 (2) a polymer film is formed from the composition applied in stage (1) PA0 (3) a transparent finish is applied to the base coat thus obtained, and then PA0 (4) the base coat is baked, together with the cover coat.
The invention also relates to a base paint for the production of the base coat of a multi-layer paint coating.
The process for production of a multi-layer paint coating on the surface of a substrate has already been known for a long time and is also described, for example, in U.S. Pat. No. 4,477,536.
It is a declared aim of the manufacturers of paint to reduce as far as at all possible the content of organic solvents, particularly in the base paints for the production of multi-layer paint coatings. The associated increase in the proportion of nonvolatile constituents results in an increase in the viscosity. When the viscosity under application conditions exceeds a certain limit, paint coatings having considerable disadvantages (blushing, poor metallic effect and poor appearance . . . ) are obtained On the other hand, the addition of substances which, by virtue of their relatively low molecular weight, only cause a relatively low increase in the viscosity results, as a rule, in inferior paint coatings, because the transparent finish incipiently dissolves the base paint (the base paint and the finish are applied by the wet-on-wet process).
The object on which the present invention is based consists, accordingly, in providing base paints which have as high a content as possible of nonvolatile constituents, without the occurrence of the above-mentioned problems.